Architecting with Service Quotas - AWS Lambda

Architecting with Service Quotas

Most serverless applications use multiple AWS services, and different services have different quotas for different features. Once you have a serverless architecture designed and know which services your application uses, you can compare the different quotas across services and find any potential issues.

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In this example, API Gateway has a default throttle limit of 10,000 requests per second. Many applications use API Gateway endpoints to invoke Lambda functions. Lambda has a default concurrency limit of 1,000. Since API Gateway to Lambda is a synchronous invocation, it’s possible to have more incoming requests than could be handled simultaneously by a Lambda function, when using the default limits. This can be resolved by requesting to have the Lambda concurrency limit raised for this account to match the expected level of traffic.

Another common challenge is handling payload sizes in different services. For an application moving a payload from API Gateway to Lambda to SQS, API Gateway supports payloads up to 10 Mb, while Lambda’s payload limit is 6 Mb and the SQS message size limit is 256 Kb. In this example, you could instead store the payload in an S3 bucket instead of uploading to API Gateway, and pass a reference token across the services. The token size is much smaller than any payload limit and may be a more efficient design for your workload, depending upon the use-case.

Load testing your serverless application also allows you to monitor the performance of an application before it is deployed to production. Serverless applications can be relatively simple to load test, thanks to the automatic scaling built into many of the services. During a load test, you can identify any quotas that may act as a limiting factor for the traffic levels you expect and take action accordingly.

There are several tools available for serverless developers to perform this task. One of the most popular is Artillery Community Edition, which is an open-source tool for testing serverless APIs. You configure the number of requests per second and overall test duration, and it uses a headless Chromium browser to run test flows. Gatling is another popular tool.